The invention relates to a carriage for a linear guiding device, designed to be arranged on a rail, said carriage comprising a center section and two legs that respectively adjoin the center section. As a result, the carriage has an essentially U-shaped cross section. In the region of the two legs, the carriage is provided with at least one roll body circuit, one return channel, a support region as well as two deflector channels that connect the return channel and the support region. Sleeve-shaped guiding means are arranged inside a basic body of the carriage, inside return channel recesses, and the guiding means are provided with a running surface for roll bodies.
Linear roll body guides are used in many areas of technology, in which one component is to be moved in a straight line, relative to another one, and if possible without any frictional losses. Machine tools represent one example for this. Guides of that type are provided with a carnage or slide, which is guided on a rail over roll bodies, such as balls, rollers or needles. The roll bodies in that case circulate in closed roll body circuits of the carriage. The roll body circuits normally have a support zone, in which the roll bodies fit against a support surface of the carriage and against a rail, thus supporting the load to be moved. As a result of the linear movement of the carriage, the roll bodies travel from the support zone to a first deflector channel, in which the roll bodies are transferred from the support zone to the return channel. Following the passage through the return channel, the roll bodies travel from a second deflector channel again to the support zone.
The use of plastic parts for the carriage surfaces that come in contact with the roll bodies has long been known, in particular for minimizing the roll body wear and for improving the quiet running of a linear guiding device. German Patent Application 35 40 099, for example, discloses the use of separately produced sleeves for the guiding surfaces of the return channel, which are later inserted into corresponding recesses in the metal basic body of the carriage. It can be considered a disadvantage with this configuration that the sleeves must be manufactured precisely and require an exact and involved assembly. Furthermore, this two-part sleeve design has additional transitions, which can reduce the quiet running.
In addition, German Patent Application 43 31 014 C2 discloses creating the guiding means in the support zones and the return channels by spraying the guide surfaces directly onto the metal basic body of the carriage with the aid of a plastic injection-molding technique. However, the shrinkage occurring in the plastic portion of the return channel when using the injection-molding technique can have disadvantageous effects on the production accuracy. Provided this is possible at all, a considerable expenditure is required to avoid or compensated these occurrences. This type of solution also requires additional anchoring points for the xe2x80x9csprayed-inxe2x80x9d sleeve on the basic body. A relatively involved lubricant supply is furthermore needed for the two previously mentioned known carriages.
Thus, it is the object of the invention to create a carriage with a simpler design, relative to its production and assembly, but which nevertheless permits a quiet running. Another aspect of the invention provides for simplifying the lubrication of the roll bodies for this configuration.
For a carriage of the aforementioned type, this object is solved according to the invention in that the guiding means for the return channels are arranged at a distance to the wall of the respective recess in the basic body, at least along a section.
With a carriage according to the invention for a linear guiding device, the guiding means of the return channel that is preferably designed as a sleeve should be arranged between bearing points and at a distance to the recess, so that a hollow space forms between the guiding means and the recess. Different from the known German reference 35 40 099, for example, the sleeve thus can bend elastically in the recess, crosswise to its longitudinal axis. The degree of bending is limited by the contact between the sleeve and the limiting surface of the recess. A movement of this type can develop, for example, as a result of vibrations or oscillations, caused by the circulating roll bodies inside the sleeve. In contrast to the standard solutions, the return channel for roll body circuits according to the invention is designed such that at least slight vibrations or deflections of the guiding means occur, if possible. Thus, vibrations are purposely taken into account and are used for achieving specific effects.
It has turned out that the elastic bending of the sleeve leads to an improvement in the quiet running of the linear guiding device according to the invention. In addition, the bending can be used for transporting a lubricant that was filled in prior to the start-up of the carriage into the space between the recess and the peripheral surface of the sleeve, over the complete length between the web regions, and which preferably fills this space completely. It has turned out that this space can be sufficiently large to make available a supply of lubricant for the respective roll body circuit, which supply is sufficient for the standard service life of linear guiding devices.
The sleeve wall of a preferred embodiment of the invention contains several openings, through which lubricant can reach the inside of the sleeve. To achieve the best possible lubricant flow, it has proven particularly advantageous if at least one of the openings is arranged in the region of the highest radial deflection for the sleeve. As a rule, this region is located in the center of the sleeve, as seen in longitudinal direction.
Despite the through openings and the elastic deflection ability of the guiding means, the cross sectional shape of the respective return channel should be as constant as possible during the circulation of the roll bodies, so as to ensure a secure and if possible low friction guidance of the roll bodies in the roll body circuit. For that reason in particular, the through openings can extend essentially crosswise to the longitudinal axis of the return channel. In addition, the longitudinal extension of each through opening should extend over no more than half, preferably one fourth, of the periphery of the guiding means.
It has proven to be useful if the guiding means is positioned in the recess in the basic body of the carriage, in the region in-between the two ends and is arranged with its complete outline at a distance to the limiting surface of the recess. As a result, particularly large deflections of the guiding means are achieved, and thus also a particularly good movement of the lubricant to the inside of the guiding means.
Finally, it is preferable if several grooves are inserted along the peripheral surface of the sleeve, which can be used as lubricant pockets. As a result, it is possible to further increase the supply of lubricant that must be inserted in-between the limiting surface of the recess in the basic body and the sleeve, without having to increase the maximum deflection ability of the sleeve. This ability is determined by the gap forming between the recess and the thickest location of the sleeve wall.
It is possible according to another useful embodiment of the invention, that the carriage is provided with a lubricant reservoir, from which lubricant is moved during the use of the carriage into the circular or sleeve-shaped gap between the recess and the sleeve. In contrast to most known carriages, the lubricant in that embodiment does not enter the area where the deflection of the respective roll body circuit occurs, but enters via the return channel.
For another preferred embodiment, plastic is poured around at least one of the two ends of the sleeve-shaped guiding means, which is a component of the deflector channel. Since the guiding means of the return channel are produced preferably together with the retaining means in the support zone, with the aid of an injection-molding technique, the plastic surrounding the sleeve-shaped guiding means on at least one end can also be connected as one piece with the support zone. As a result, the guiding means of the return channel can be centered and secured in the return channel with the same injection molding operation, in which the retaining means and the corresponding part of one or both return channels of a roll body circuit are also produced. In addition, a predetermined distance between the longitudinal axis of the return channel and a longitudinal axis of the support zone can also be maintained particularly easily in this way.
Further preferred embodiments of the invention follow from the description below.